Posting an image of the flag online, the embassy said: "The US Embassy joins all Americans, Irish, and people around the world in expressing our condolences to the victims and families of the horror attack in Las Vegas.

"If you’d like to leave a message of condolence, please do so below."

The gunman has been named as Stephen Paddock, who opened fire from the 32nd floor of the Mandalay Bay Casino while crowds were enjoying the Route 91 Harvest country music festival.